Process for increasing the carbon chain length of an olefin



PROCESS FOR INCREASING THE CARBON CHAIN LENGTH OF AN OLEFIN William von E. Doering, New Haven, and Paul M. La

- Flamme, New Britain, Conn., assignorsto The Carwin Company, North Haven, Conn., a corporation of Connecticut No Drawing. Application March 9, 1959 Serial No. 797,836

2z or. 260-680) a The present invention relates to an organic synthesis, and more particularly to a process for increasing the carbon chain length of an olefin by one carbon atom.

Heretofore, various processes have been developed for increasing the carbon chain length of organic compounds. For example, the carbon chain length of olefins has been 2,933,544 I PatentedApr. l9, 1 96 0 olefin at the double bond thereof in accordance with the following equation:

This reaction is conducted in the absence of a reaction medium. In the reaction a large excess of the olefin,

, i.e., from 3 to 6 moles, 1 mole of potassium tertiary increased by means of polymerization processes wherein the olefinic monomer is converted to a dimer, trimer, tetramer, or higher polymer. Such polymerization processes, however, cause a multifold increase in the carbon In general, the process of the invention comprises reacting together a haloform, an alkoxide, and an olefin to form a halocycloalkane, and reacting the halocycloalkane with a metal to form an acyclic olefin containing one more carbon atom than was present in the initial olefin. In particular, the process of the invention for increasing the carbon chain length of an olefin by one carbon atom comprises reacting together bromoform, potassium. tertiary butylate, and an olefin having the general formula Y where R R R and R represent hydrogen or an alkyl radical having from 1 to 8 carbon atoms and may be the same or difierent to form a 1,1-dibromocyclopropane having the general formula where R R ,'R and R; are as above, and reacting the LI-dibromocyclop'ropane with an active metal, such as sodium, magnesium, zinc or aluminum, to form an olefin having the general formula where R R,, R; and R, are as above.

The reaction between bromoform, potassium tertiary butylate, and the olefin causes cyclization and bromination of the olefin by addition of dibromocarbeue to the butylate, and 1 mole of bromoform are used. The reaction is conducted by adding the solid potassium tertiary butylate to the reaction vessel and then adding the liquid or liquified olefin thereto to dissolve the potassium tertiary butylate. The last reactant to be added to the reaction vessel is the liquid bromoform which is slowly added thereto. The reaction is conducted at a low temperature by subjecting the reactants to a cooling medium maintained between 20 C. and 10 C.

'The 1,1-dibromocyclopropane can be worked up and recovered from the reaction mixture by washing the mixture with water to dissolve the potassium bromide byproduct precipitant and to form an aqueous layer and an organic layer. After separation of these two layers, for example, by use of a separating funnel, the water extracts are washed with pentane, the pentane solution separated from the aqueous solution and added to the first organic phase. The combined organic layers are then dried over a suitable drying agent, such as sodium sulfate, to remove any traces of water. The 1,1-dibromocyclopropane is then recovered from the combined organic phases by fractional distillation at an appropriately reduced pressure dependent upon the boiling point of the 1,1-dibromocyclopropane. v

Thereaction between the 1,1-dibromocyclopropane and the active metal results in the debromination or elimination of both bromine atoms from the 1,1-dibromocyclopropane with the formation of a metallic bromide byproduct and the cleavage of the cyclopropane ring to form an olefin containing one more carbon atom than the initial olefin, in particular a diolefin containing cumulative double bonds and called an allene, in accordance The allenes are of considerable interest because of their optical properties and their use in the preparation of polymers, ketones and acetylenic compounds.

The reaction between the 1,1-dibromocyclopropane and theractive metal is conducted in the presence of a solvent or reaction medium when the active metal used is magnesium, zinc or aluminum. The reaction medium must be anhydrous, inert under the reaction conditions, and

separable from the reaction products, for example, by distillation. Typical suitable reaction media include diethyl ether, tetrahydrofuran, and cis-decalin. A reaction medium need not be employed when the active metal is sodium, for example, a high surface dispersion of sodium on 31 g t by the followingexamples,

Equivalent weights of the Ll-dibromocyclopropane in order to prevent rearrangement of-the allene product into an acetylene isomeric; therewith. In general, it is preferred that when the reaction is conducted. in the} presence of a reaction. medium that the active metal be present in an excess of no more than 20%. When the reaction is conducted in the absence of a reaction medium, a largeexcess" of active metal may be utilized, since there is no danger under these-conditions of the allene product rearranging into an acetylene. V

The active metal mustbe ina. finely divided form, for example, powder, dust, granules, flakes... lt Y ngs,,liling S,; t r s a e The. order of addition of. the two, reactants to. one another is immaterial, although it. is preferred toadd the. 1,1- dibromocyclopropane; to. the active metal; Moreover, with the less, reactive metals, such as. aluminum. and zinc, the reactants and reaction medium may be. mixed Oi gether and then heated to initiate the reaction rather than adding one. reactant, to. another.

The temperature during the; reaction; conducted 'in the presence. of.a reaction mediumis such as to, initiate a the reaction and to keep the reaction mixture under. gentle. rcflux until the. reaction, is complete vvlili'ch'gv may". from about 1 to. 18. hours. or, longer. dep'endiu'gupon the reactivity ofi thereac'tants' When'tliel reaction is cond ucted, in. the absence. of a reaction medium and using, a dispersion. of sodium on alum na, the; reaction. proceeds" quite rapidly at room temperature and may havefto be. cooled to avoid'distilla'tion. of the 1,,L-dibromocyclo propane reactant while permitting. distillation of the' ol'efinic or allene; product. The. reaction. using. surface dispersin, of sodiumon alumina, either in. thepresen'ceor absence of a reaction medium, may be conducted underreduced pressure, for example, a pressure of 2.

millimeters t0f25. millimeters of mercury, to distill the."

allene productf'rom the, reaction mixtureas, fast as, possible.

It is. preferred. to. conductthe reaction addin 3 -LL-dibromocyclrjpropane to, a. high surface dispersion of. sodium. on alumina, since. in this matter theolefini'c or.

aliens: Product, is readily. recovered from the reaction.

reaction... whenithereactiou i'seonductedl by gently res.

fluxing the. reactants and productsin the.,presenc'e, of a reaction medium, the olefinic. or alleneproduct' may be. recovered from .the reactionjmixture after. completionof. the reaction in the following manner. The excess active metal is filtered off from the reaction mixture. The reaction mixture is then washed with water to extract the metallic bromide by-produ'c't therefrom' and. the aqueous metallic bromide phase thenseparated from, the reaction 4 emu methanol bath and equipped witha Dry Ice reflux condenser, dropping funnel, and magnetic stirrer, and 17' grams (0.30 mole) of cis-butene added thereto. The

' temperature of thebath w'as then adjusted and mainreaction is conducted in the presence of a reaction medium 7 tained between 20 C. and; L0 .C. while 12.7 grams "(0.050 mole) of bromoform was added dropwise to the stir-red solution over ithe course: of 20i 'miuutesi After.

standing an' additionatfli)" minutes; the solution was washed twice with. an ual volume. of water; the water.

extracts weretheu washed with 10. milliliters of penta'ne and the, combined organic layers were: driedover sodium sulfate. The cis-dibromo-2,3-dimethylcyclopropane'prodnot was recovered from the organic layers by fractional distillation" ata reduced. pressure. 1

Part B warming and was essentially complete after two: hours under. gentle reflux.

Theolefinic or allene product was recovered from the 7 reaction mixture. as" follows. 'The' excess magnesium 'turnings were se'p'arated from the. reaction mixture by filtration. The reaction mixture was then washed with ,water. to extract. the. magnesium bromide lay-product therefrom and the aqueous magnesium bromide phase 1 then separated bymea'n's; Ofa' separately funnel from' the ether. phase containing the. olefinic or allene product. A

trace of flydrfo'qu'inone was added to; the" ether phase to preventpoly'rnerizatibn ofgtlreolefrnic or allene product:

The. ether phase-was. dried with magnesium sulfate to re movetrlacesof water therefrom and then the driedetherphase. fractionated through a" teninch helix-packed colurnn giving. L8 grams of a first fraction having a boiling pointrange of 40 -46 6., 0:60 gram-of a secondrfraction having. a boiling point range of 46.0-48.0 C, and 1.60

' grams of a third fraction havingaboilingpoint rangeof.

48-4 9 C. Redistillation of this third fraction, whose: infrared spectrum showed a very strong peak at 5.06 microns characteristic of allenes, gave a 16% yield of 2,3- pentadiene or 'LB-dimethyIalIene. (symmetrical dimethyllfl a therefnonl 1 I allene) having a point a C. at a preswas placed in the apparatus of Example 1, Part A, and

medium containing the olefinic or alle'ne product. A

trace of a polymerization inhibitor, such as hydroquinone, may then be added to the reaction medium phase containing the olefinic orallene product in order to prevent polymerization thereof. Thereaction mediumphase. a

is then dried. witha suitable. drying agent, such as mag nesium sulfate, to remove any trace ofwa'ter'present there in. Theolefinic. or. alljenepreduetsis then separated from R x mpl by; fractional distillation 17 grams (0.24 mole) of l-pentene added thereto. The temperature of the bath was. then adjusted and maintained between -20 C. and 10 C. while 12.7 grams (0.050 mole) of bromofo'rm. wasradded dropwise to the stirred solution over the course of 20 minutes. After standing an additional 30 minutes, the reaction mixture was worked up and the l,1-dibromo-Z-n-propylcyclopropane produet: recovered. in. the manner: set forth abovev infixampleh Pandait had. a. bnuinen i h 6319* :.0 anapressureof lllmillimerersofmercuny and The. proce s oi he. inven ion. will heilli s ratcd Bart A 6.2 grams (-0.055Imole) of potassium. tertiary. butyliatc was placed in an Erlenmeyer flask immersed imaDm-Iec:

its index of refraction was-1.11 Part B v V V -A solution of 24.2 grams (O.1. .mole) of 1,1-dibromo- .fZ-n-propylcyclopropane in 2'Smil1iliters of anhydrous diethyljether was added? slowly to 2.67 grams (0.11 gram atom) of magnesium turnings in 25 milliliters of anhydrous diethyl. ethcr in the apparatus ofExample. l, 1 Paris B. After gentle reflux, the:- re actionlimixture was workedvup in the; manner set forth; above-in Example. 1,. Bart: B,,'giying. 2.65.: gramsofl 1 -,2i hexadiene or Il-QIOPYL- mat-1min.- a boiling point of 74-75 c. and'a very strong peak in its infrared spectrum at 5.09 microns characteristic 'ofallenes and 11.23 grams of recovered starting material for a yield of 62% based on unrecovexedstarting material. A

' EXAMPLE 3 Part A 6.2 grams (0.055 mole) of potassium tertiary butylate was placed in the apparatus of Example 1, Part A, and 17 grams (0.24 mole) of 2-methyl-2-butene added thereto. The temperature of the bath was then adjusted and maintained between 20 C. and 10 C. while 12.7 grams (0.050 mole) of bromoform was added drop wise to the stirred solution'over the course of 20min= utes. After standing an additional 30 minutes, the reaction mixture was worked up and the 1,1-dibromo- 2,2,3-trimethylcyclopropane product recovered in the manner set forth above in Example 1,' Part A. It had a boiling point of 40-50 C. at a pressure of 8 millimeters of mercury and its index of refraction was u 1.5134.

Part-B tetrahydrofuran in the apparatus of Example 1, Part B. After gentle reflux, the reaction mixture was worked up in the manner set forth above in Example 1, Part B, giving 1.72 grams of starting material and 2.75 grams of 2-methyl-'2,3-pentadiene or 1,1,3-trimethylallene having a boiling point of 725 C. and a peak in its infrared spectrum at 5.09 microns for a yield of 34%.

EXAMPLE 4 Part A 6.2 grams (0.055 mole) of potassium tertiary butylate was placed in the apparatus of Example 1,,Part A, and 17 grams (0.15 mole) of l-octene added thereto. The temperature of the bath was then adjusted and maintained between -20 C. and '10 C. while 12.7 grams (0.050 mole) of bromoform was added dropwise to the stirred solutionover the course of 20 minutes. After standing an additional 30 minutes, the reaction mixture was worked up and the 1,1-dibromo-2-hexylcyclopropane product recovered in the manner set forth above in Example 1, Part A. Part B In the apparatus of Example 1, Part B, modified by using a 1 liter three-necked flask rather than a 500 milliliter three-necked flask there was placed 73 grams (0.3

.gram atom) of magnesium turnings, 800 milliliters of anhydrous diethyl ether, and 1 gram of 1,1-dibromo-2- hexylcyclopropane. After warming slightly to initiate the-reaction, the remainder of 23.2 grams (a total of 24.2 grams or 0.10 mole) 1,1-dibromo-2-hexylcyclopropane was added with stirring at a rate sufficiently rapid to cause gentle refluxing. After the addition was completed, refluxing was continued for a further hour. The reaction mixture was worked up in the manner set forth above in Example 1, Part B, giving a 61% yield .of 1,2-nonadiene or hexylallene.

EXAMPLE 5 A Part-A 1,1-dibromo-Z-hexylcyclopropane was prepared and (0.1 mole) of l,l-dibromo-2-hexylcycl0propane. The reaction mixture was refluxed gently for 18 hours and then worked up in the manner set forth above in Example 1, Part B, to givea yield of 61% of 1,2-nonadiene or hexylallene.

EXAMPLE 6 Part A 1,1-dibromo-2-hexylcyclopropane was prepared and recovered in the manner set forth above in Example 4, Part A. i

Part B In the apparatus of Example 4, Part B, there was EXAMPLE 7 Part A 1,1-dibromo-2-n-propylcyclopropane was prepared and recovered in the manner set forth above in Example 2, Part A.

Part B A high surface dispersion of sodiumon alumina was prepared as follows: 103 grams of chromatographic alumina of -200 mesh was dried at 500 C. for 15 hours,- cooled and placed in a 500 milliliter three-necked flask equipped ,with a mechanical stirrer where it was further dried at 200 C. for 2 hours while stirring at a reduced pressure of 1 millimeter of mercury. The flask was cooled to 150 C. and, under nitrogen, 14.0 grams (0.61 gram atom) of sodium powder was added. Stirring was continued until a dark gray dispersion formed.

An addition funnel and an exit tube connected to a trap at -78 C. were attached to the flask; At a reduced pressure of 5 millimeters of mercury 24.2 grams (0.1 mole) of l,1-dibromo-2-n-propylcyclopropane was added dropwise with stirring at room temperature. The

EXAMPLE 8 Part A 6.2 grams (0.055 mole) of potassium tertiary butylate was placed in the apparatus of Example 1, Part A, and 17 grams (0.30 mole) of trans-butene added thereto. The temperature of the .bath was then adjusted and maintained between 20 C. and 10 C. while 12.7 grams (0.050 mole) of bromoform was added dropwise to the stirred solution over the course of 20 minutes. After standing an additional 30 minutes, the reaction mixture was worked up and the trans-1,l-dibromo-2,3-dimethylcyclopropane product recovered in the manner set forth above in Example 1, Part A.

nan Y A high surface dispersionof 14.0 grams (0.61 gram atom) of sodium on 70 grams of dried alumina was prepared as set forth above in Example 7, Part B. Into the apparatus of Example 7, Part B, milliliters of anhydrous cis-decalin was added. Thereupon, a. solution 02537.0 (0.25 mole) of trans-1,1-dibron'io-2,3 di-' rdethylcyclopropane in 0 milliliters' of anhydrous cis deeaun Was-added ilropwise with stirring overl'a period (Sf- 2% liofirs -at 'a pressure ot 25 millimeters of mercury and at room temperature The exothermicareaction-was cooled intermittently to maintain rhe reaction mixture at 35 C. After an additional hour, the trap had collected 17.6 grams of liquid from'which 7.46 grams (44%) of organ olefin by'one'carbon gether ubromoform, potassium; tertiarygbutylatep and g1 p'entene to .form 11A;dibromo-2wnqiropylcyclopropane and reactingsaid 11,1-dibromo 2-n propylcyclopropnne nearly pure-lfi-pentadiene 01' 1,3*-'dimethylallene having' a boilmg point in the range 'of 48.O-*48;5 C. and a very strong peak in the infrared at'5.09 microns was obtained by fractional distillation.

' "EXA-"MPLE 9 -Part-A' I V l1 dibrofno LheXyleyclopropane 'was prepared :and recovered --in the "manner set forth above imEXam'ple 4, Part Y Part-B 'A high surface dispersion of 117.3 grains (0.75 gram atom) of sodium on l50;grams"of dried alumina was prepared as set forth above in Example 7, Part B. ,In

the apparatus of Example 7, Part B, therewas added dropwise'with 's'tirring 7 1 grams {0.25 mole) of lil-dibromo-2 -hexylcyclopropa'ne at Zmillimeter pressure. An

87% yield of 1,2-nonadiene or hexylallene havingea boiling point of'l52" C. was recovered from the trap by fractional distillation.

This IQPPHCBUODJS a continuation in-part of applicawhere R R Rg, and-R are radicals selected from the group consisting of hydrogen and wan alkyl radical having from -1 to 18 carbon atoms to form a 1,1-dibromocyclopropane having the general formula R4 7 where R R ,-R and Rgare as above,'l and reactingisaid 1,l-dibrorriocyclopropane with "a metal selectedfrom the group co'nsisting Iof sodium, magnesium, zinc, and aluminum' to form' an olefin havingtthegeneral formula 2.- The 'proces's for 1 increasing "the carbon "chain length of an olefin by one carbonatom-'comprisingreactingtogether bromoform, potassium tertiary butylate,v and cisbutene to form cis-dibromo 2,3-dimethylcyclopropane,

and 'rea'cting said 'cis dibromm2;3 dimethylcyclopropane with a metal selected from the group consisting of "so- 'dium, ma gnesium zinc, and aluminumto form 2,3-pentadiene or 1 l ,3dimethylallene.

witlra metal selected from theigroupwon'sisfinsiofreofi dium, magnesium, zine, and aluminum to form 1,2 hexadiene or napropylallene." I i 4. The process for increasing the carbon chain length ofwan olefin -by one carbon atom comprising reacting togeiher bromoform, potassium tertiary 'butylate, and methyl-lbutene toform 1.,-1 dibromo-2,Z3-trimefl1ylcyclopropane, and reacting said 1',1-.dibromo-2,2,'3-triniethyl-. cyclopropane with a metal selected from the group con-T sisting of:sodium, magnesium, zinc, and aluminum to form 21methyl-2,3! pent adiene or 1,1,3-trimethYlallene.

5. The process for increasing the carbon Y chain length of ane olefin by one carbon,atomlcomprisingereacting together brornoform, potassium tertiary hutylate; and '1 'octene to form 1,l dibromo 2-hexylcyclopropane,rand-re; acting said 1,1-dibromofirheirylcyclopropane with .ametal selectedfrom thegrbup consisting ofgsodium, magnesium, zinc, and aluminum to form 1,2-nonadiene or hexylal'lene.

6. The process for increasing the carbon chain length of an olefin by onev carbon atom comprising reacting together f'bromdformypotassium tertiary butylate, and trans-butene toform trans- 1;1 dibromo-Z,'3-dimethylcyclopropane, and reacting said 'trans 1,1 dibromo 2;3 dirneth ylcyclopropane with ameta'l iselected :fromfthe group tion-Serial N0. 116;863,'fi1ed February 24, 1958, now

consisting or sodium, magnesium, zinc, and aluminum t form 2,3-pe'ntadieneor l,3 ='t'limet'hylallene.

- "7. The process for "the preparation of'an allenecomprising reacting 'a :lQl-dibrbmotylopropane having 'the general formiila from 1 to 8 carbon atomswith a metal selected'from the group consisting-of flsodium, magnesium, zinc, and :aluminum.

8. The ,process as set .lforth 'in claim 7 wherein the metal'is sodium in the form-of its high surface disperjsion onalurnina. i

9'.- The process 'for the preparation of ZB-pentzidiene (1,3-dimethylallene) comprising reacting '1,'1-dibromo 2;3- dimethylcyclopropane with magnesium.

' 10. The'process for the preparation ofFIQeheXadiene (n-propylallen'e) comprising reacting l,1-dibromo-2=npropylcyclopropane with magnesium.

' -3. The process-for increasing the carbon chain length 35 11. The process for thepreparation of '2'-methyl -2 ;3 penta'diene (1,1,3-tri1'n'ethylallene) comprising reacting 1; dibromo-ZQ,3-trimethylcyclopropane with magnesium.

12. The process forthe preparationof 1,2-heXadiene (n-pro'pylallene) comprising reacting l,l-dibromo-2 npropylcyclopropane'with'sodium. Y a 4 "l3. Theprocessffor the 'preparat'ion of-2,-3 pentadiene (l,3-dimethylallene) comprising reacting 1 l-"dibromo '2i3 dimethylcyciopropane with sodium.

'14. The process for the preparation of 1; 2-nonadiene (heylallene) comprising reacting- "lfl-d-ibrorno lhexylcyclopropane with sodium. 7

15. The process for the preparation of an allene comprising reacting in ananhydrous inert solvent at 1,1-di- -bromoeyelopropanehavingilreigeneralfformula where R R R and R are radicals selected from the group consisting of hydrogen and an alkyl radical having from 1 to 8 carbon atoms with a substantially equivalent weight of a finely divided metal selected from the group consisting of sodium, magnesium, zinc and alumimum at a temperature to keep the reaction mixture under gentle reflux.

16. The process for the preparation of an allene comprising reacting in the absence of a solvent a 1,1-dibromocyclopropane having the general formula where R R R and R are radicals selected from the group consisting of hydrogen and an alkyl radical having from 1 to 8 carbon atoms with an excess of finely divided sodium in the form of its high surface dispersion on alumina at room temperature and under reduced pressure.

17. The process for the preparation of 2,3-pentadiene (1,3-dimethyla1lene) comprising reacting in an anhydrous inert solvent l,l-dibromo-Z,3-dimethylcyclopropane with a slight excess of finely divided magnesium at a temperature to keep the reaction mixture under gentle reflux.

18. The process for the preparation of 1,2-hexadiene (n-propylallene) comprising reacting in an anhydrous inert solvent 1,l-dibromo-2-n-propylcyclopropane with a slight excess of finely divided magnesium at a temperature to keep the reaction mixture under gentle reflux.

19. The process for the preparation of 2-methyl-2,3- pentadiene (1,1,3-trimethylallene) comprising reacting in an anhydrous inert solvent 1,1-dibromo-2,2,3-trimethylcyclopropane with a slight excess of finely divided magnesium at a temperature to keep the reaction mixture under gentle reflux.

20. The process for the preparation of 1,2-hexadiene (n-propylallene) comprising reacting in the absence of a solvent 1,l-dibromo-2-n-propylcyclopropane with an excess of finely divided sodium in the form of its high surface dispersion on alumina at about room temperature and under reduced pressure.

21. The process for the preparation of 2,3-pentadiene (1,3-dimethylallene) comprising reacting in an anhydrous inert solvent l,l-dibromo-2,3-dimethylcyc1opropane with an excess of finely divided sodium in the form of its high surface dispersion on alumina at about room temperature and under reduced pressure.

22. The process for the preparation of 1,2-nonadiene (hexylallene) comprising reacting in the absence of a solvent 1,1-dibromo-2-hexylcyclopropane with an excess of finely divided sodium in the form of its high surface dispersion on alumina at about room temperature and under reduced pressure.

References Cited in the file of this patent Doering et al.: J. Amer. Chem. Soc., vol. 76, pages 61, 62-5 (1954).

UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent N08 2933544 April 19 1960 William Von E9 Doering et ale It is hereby certified'that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

' 2 Column 4, line 65 and column 5, line .21 for n each D column 8 line 65 for (heylallene)" occurrence, read me n 5 read me (hexylallene) "=0 Signed and sealed this 27th day of June 1961a (SEAL) Attest:

ERNEST W. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents 

1. THE PROCESS FOR INCREASING THE CARBON CHAIN LENGTH OF AN OLEFIN BY ONE CARBON ATOM COMPRISING REACTING TOGETHER BROMOFORM, POTASSIUM TERTIARY BUTYLATE, AND AN OLEFILN HAVILNG THE GENERAL FORMULA
 7. THE PROCESS FOR THE PREPARATION OF AN ALLENE COMPRISING REACTING A 1,1-DIBROMOCYCLOPROPANE HAVING THE GENERAL FORMULA 